::SNICKER:: I quite enjoyed this lightly fleshed out bunny. It seems to fit what we see in canon of pureblood attitudes and their ending their own culture seems quite in keeping with what could happen without a leavening of new blood and thinking (one can point to various companies and organizations where something similar has led to great falls).
Author's response
Thanks! to me, the least likely part of the story was the Purebloods actually agreeing on a definition of 'pure-blood'